I’m frequently contacted by amphibian keepers who find that their pets are floating about at the water’s surface and seem unable to submerge. While gas produced by bacteria within the animal can cause this, the most frequent culprit is Gas Bubble Disease. This term is sometimes used to refer to any of several related but different maladies, and commonly afflicts African Clawed Frogs (Xenopus laevis), Dwarf Clawed Frogs (Hymenochirus spp.) and Mexican Axolotls (Ambystoma mexicanum).
How it Occurs
Gas Bubble Disease usually arises when water becomes supersaturated with oxygen, carbon dioxide or other common gases. The usual way for a supersaturated condition to occur in captivity is via air introduced through leaks around pumps, tubing or valves, or as a result of overly-powerful aeration.
In a supersaturated environment, bubbles (termed emboli) may form in the blood or tissues of an amphibian. These bubbles may sometimes be seen just below the skin, in the eye, or in the webbing between the toes. They may also congregate in the abdomen, causing it to swell. Death eventually results from the internal accumulation of gas.
Also, capillaries usually rupture and the skin around the bubbles may break down, leaving the animal open to a bacterial (i.e. Aeromonas hydrophila) infection. In fact, such infections, often termed red leg, are usually fatal even before the disease has run its course.
Removing Gases from Water
Gases may be removed from large systems by allowing water to enter the system via a spray, and then to trickle through 4-foot-high PVC pipe filled with small stones. I found this to be very effective in large exhibits at the Bronx Zoo. This set-up can also be used as a pretreatment for water to be used in smaller aquariums.
Reducing the amount of air entering the aquarium by sealing leaks in hoses and cutting back on the filter’s outflow or the pump’s power is also useful.
If action is taken quickly, afflicted animals may recover. However, even if the bubbles disappear and your pets seem fine, they should be seen by a veterinarian to rule out the presence of a bacterial or fungal infection.
The abstract to an interesting article on Gas Bubble Disease in frogs is posted here.